Preheat the grill. Season rib eye steaks on both sides with salt and pepper. Grill rib eye steak to medium-rare, about 4 minutes on each side. Remove steak from grill and let rest for 10 minutes. Slice the steak into thin ½-inch thick strips, discarding any fat and set aside.
Preheat the broiler to medium-high. Add about ¼ cup of the olive oil to a shallow dish and dip one of the cut sides of each baguette slice in the olive oil, then arrange the slices, oil-side up on a baking sheet. Broil them just until golden brown, about 1 minute.
Place a small saucepan over medium-low heat. Add the Boursin cheese and about 2 teaspoons of water, using the back of a spoon to break up the Boursin cheese. Stir continuously until the cheese has completely melted, making sure that the cheese does not burn. Once melted, remove from heat and set aside.
To serve: place the crostini on a serving platter and place a small piece of steak on each piece. Top each with a spoonful of the Boursin cheese. Garnish with micro-greens (optional).