The Chairboys, searching for their first league victory since 13 August, showed promise in a quiet opening period to the game with Michael Harriman's free-kick producing an excellent save from Jamie Jones.
The hosts then went close again with Southwell failing to convert a gilt-edged chance on the stroke of half-time.
Southwell however went from villain to hero moments later as the forward tapped home Sam Wood's cross in the third minute of first-half stoppage time.
Both sides upped the tempo in the second half and a strong midfield battle ensued, but the Chairboys were able to resist Stevenage with Andrew Fox spurning the best opportunity for the visitors.
Indeed, though the Boro dominated the latter stages of the game, a barrage of long balls came to nothing as the home side saw the game out to record their second league victory of the season.
Report supplied by Press Association.
Match ends, Wycombe Wanderers 1, Stevenage 0.
Second Half ends, Wycombe Wanderers 1, Stevenage 0.
Corner,  Wycombe Wanderers. Conceded by Charlie Lee.
Paris Cowan-Hall (Wycombe Wanderers) wins a free kick on the left wing.
Foul by Kgosi Ntlhe (Stevenage).
Substitution, Wycombe Wanderers. Dan Rowe replaces Sam Wood.
Foul by Garry Thompson (Wycombe Wanderers).
Fraser Franks (Stevenage) wins a free kick in the defensive half.
Attempt missed. Tyler Walker (Stevenage) right footed shot from the right side of the box is close, but misses to the right.
Attempt missed. Dominic Gape (Wycombe Wanderers) right footed shot from outside the box is close, but misses to the right.
Anthony Stewart (Wycombe Wanderers) wins a free kick in the attacking half.
Foul by Tyler Walker (Stevenage).
Michael Harriman (Wycombe Wanderers) wins a free kick in the attacking half.
Foul by Rowan Liburd (Stevenage).
Substitution, Stevenage. Rowan Liburd replaces Michael Tonge.
Attempt saved. Paris Cowan-Hall (Wycombe Wanderers) right footed shot from the left side of the box is saved in the bottom left corner.
Corner,  Wycombe Wanderers. Conceded by Charlie Lee.
Paris Cowan-Hall (Wycombe Wanderers) is shown the yellow card for a bad foul.
Foul by Paris Cowan-Hall (Wycombe Wanderers).
Kgosi Ntlhe (Stevenage) wins a free kick in the defensive half.
Foul by Michael Harriman (Wycombe Wanderers).
Ben Kennedy (Stevenage) wins a free kick on the right wing.
Attempt saved. Paris Cowan-Hall (Wycombe Wanderers) right footed shot from the left side of the box is saved in the top centre of the goal.
Substitution, Wycombe Wanderers. Paris Cowan-Hall replaces Dayle Southwell.
Substitution, Stevenage. Jobi McAnuff replaces Tom Pett.
Attempt saved. Dayle Southwell (Wycombe Wanderers) header from the centre of the box is saved in the centre of the goal.
Dominic Gape (Wycombe Wanderers) wins a free kick in the attacking half.
Foul by Michael Tonge (Stevenage).
Corner,  Wycombe Wanderers. Conceded by Charlie Lee.
Attempt saved. Sam Wood (Wycombe Wanderers) header from the left side of the box is saved in the centre of the goal.
Attempt missed. Anthony Stewart (Wycombe Wanderers) header from the centre of the box is just a bit too high.
Corner,  Wycombe Wanderers. Conceded by Fraser Franks.
Paul Hayes (Wycombe Wanderers) wins a free kick on the left wing.
Foul by Ben Kennedy (Stevenage).
Substitution, Stevenage. Ben Kennedy replaces Andrew Fox.
Attempt missed. Andrew Fox (Stevenage) left footed shot from the centre of the box misses to the right.
Hand ball by Dominic Gape (Wycombe Wanderers).
Aaron Pierre (Wycombe Wanderers) wins a free kick in the defensive half.
Foul by Tyler Walker (Stevenage).
Corner,  Stevenage. Conceded by Aaron Pierre.
Dayle Southwell's first-half goal was the difference as Wycombe Wanderers edged past Stevenage at Adams Park.