For the 1999 Subaru Legacy, both the low-beam and high-beam headlights use a 9007 bulb. The fog light fitment requires comparison with the original bulb: the listed options are H3 and H3C.
Other exterior lighting includes 1157 or 198 bulbs for the front turn signals and parking lights, 1156 for the rear turn signals and reverse lights, and 1157R for the brake and tail lights. The front side marker uses 1157A, while the rear side marker uses 168NA.
Check the original bulb before ordering for the center stop light, which may use 921 or 912. License plate lighting also has multiple listed options: 168, 917, 194, or 7441, depending on the original setup. Interior applications include DE3175 for the dome and map lights, 158 for the courtesy light, and 912 for the trunk light.