Stack panini bread on a cutting board and cut in half. Spread the spinach basil pesto on cut side of each piece of bread.
Lightly brush oil on a sheet pan. Fill the sheet pan with half of the panini bread halves (pesto side up).
Top each with 2 slices of tomato. Divide mozzarella cheese on top. Cover with second half of panini bread (already with basil mixture on it). Lightly brush the outside of the bread with olive oil and bake at 375 degrees, until toasty.