26 appearances as a relief pitcher. He ended his rookie MLB campaign with a 3.29 earned run average, four saves and 52 strikeouts in 63 innings pitched. But he was less effective in , with his ERA climbing to 5.52 in only 29 innings of work, and spent part of the season back at Triple-A Tacoma. In the expansion draft of October 1968, Stoneman was selected by the Montreal Expos, where he spent five seasons and became a full-time starter for manager Gene Mauch. He threw his two no-hitters with the Expos: the first against the Philadelphia Phillies at Connie Mack Stadium on April 17, 1969. It was Stoneman's fifth major league start and only the ninth game of the franchise's existence; he had eight strikeouts and five walks. The second came at the end of the 1972 season on October 2, when he defeated the New York Mets in Montreal at Jarry Park, caught by Tim McCarver. The latter was the first major league no-hitter in Canada, and both were 7–0 scores. The second included nine strikeouts and seven walks. Stoneman also threw a one-hitter at home in 1971 against the San Diego Padres, a well-attended 2–0 win on Helmet Night on Wednesday, June 16. In perhaps the best outing of his career, Stoneman struck out 14 and allowed just one base on balls. The only hit came with one out in the seventh inning, a clean single to right field off the bat of Cito Gaston, which was the Padres' only well-struck ball of the night. He was named to the National League All-Star Team in 1972 and pitched two innings in relief with two strikeouts. At tall and , Stoneman was a workhorse who over four consecutive seasons (–) logged more than 200 innings pitched. He struck out 251 in 295 innings in 1971, with a 17–16 record and a 3.15 ERA for non-contending Montreal(71–90 ()). That season, Stoneman also finished third in strikeouts in the National League, behind Tom Seaver (289) and Ferguson Jenkins (263), and his 39 starts tied for the league-high with Jenkins. He also had 20 complete games in 1971, tied for third with Bob Gibson. His career was shortened by an arm injury in 1973: his earned run average ballooned from 2.98 in 1972 to 6.80 (1973), then 6.10 (1974), for a record of only 5–16 in that span. Overall, Stoneman won