Large Igneous Provinces are like Lunar Mare?
I disagree with Michael about the "not as large as the lunar mare" part. Head and Wilson (1992) mention that the "total area of exposed mare deposits is about 6.3 millions km2" (17 % of the Moon's surface area). They estimated a total volume of 10 millions km3. The largest mare, Oceanus Procellarum, covers about 4 millions km2.

These values are quite comparable with Large Igneous Provinces (LIPs) in terms of area, and are even one order of magnitude lower in terms of volume. From the Encyclopedia of Volcanoes:


  The composite Ontong-Java-Manihiki-Hikurangi plateau covers 3.5
  million km2 with an estimated volume 59-77 million
  km3. [...] The Kerguelen plateau in the southern Indian
  Ocean is the second largest LIP, covering 2.3 million km2
  with a volume of 15 million km3 [...] Not all LIPs are
  oceanic plateaus; for example, the North Atlantic volcanic province,
  derived from a hot spot presently centered beneath Iceland, has an
  area of 1.3 million km2 [...] Also notable are the Deccan
  traps in India (1.8 million km2/9.3 million
  km3).


If lunar maria seem that large from Earth, it's only because the Moon is small!

But to know if lunar maria or LIPs would have looked like "glowing lava oceans shinning in the night", we need to look at emplacement rates rather than just areas and volumes. From the same chapter, one can calculate LIP emplacement rates of ~3-13 km3 per year. It may seem quite low (for comparison, ocean ridges quietly produce ~20 km3 per year), but it is an average output rate over a few million years. As noted on largeigneousprovinces.org, their might be pulses of magmatic activity, with peaks in production rate. This is exactly what's been inferred for lunar maria by Wilson and Head (2017): even if the average output rate has been calculated at a very low 0.01 km3 per year, they found that some flows could have been emplaced with rates up to 106 m3s-1!

As to whether this would have been visible from space: define "from space"! From low Earth orbit like the ISS? From the Moon itself? :)