Preheat the grill or broiler.
Heat the oil and butter in a large skillet over medium-high heat. Add the onions and peppers and cook over high heat for 4 minutes. Stir in the minced garlic, cook for 30 seconds, then add the tomatoes. Simmer 5 minutes until thickened. Remove from heat and season to taste.
Grill the bread for 2 minutes on each side, then rub 1 side of each slice with the cut side of 1/2 of a garlic clove. Top each slice of bread with a heaping spoonful of the pepper mixture, sprinkle with basil and serve immediately.